Monitoring head wear

ABSTRACT

A method, executed by a computer, for monitoring head wear includes reading from a cartridge a high frequency pattern and a low frequency pattern, determining a first read amplitude corresponding to the high frequency pattern and a second read amplitude corresponding to the low frequency pattern, and determining a head wear metric according to the first read amplitude and the second read amplitude.

BACKGROUND OF THE INVENTION

The present invention relates generally to magnetic tape data storage,and more specifically, to monitoring the condition of tape heads.

In the field of magnetic tape data storage, tape heads are a type oftransducer used to convert electrical signals to magnetic fluctuationsand vice versa. Tape heads may be used to read, write, and/or eraseinformation to/from magnetic tape storage. Over time, tape driveoperation may wear down a tape head, leading to higher error rates andeven drive failure. One way to monitor head wear is to gather data onthe head-to-tape spacing.

SUMMARY

As disclosed herein, a method, executed by a computer, for monitoringhead wear includes reading from a cartridge a high frequency pattern anda low frequency pattern, determining a first read amplitudecorresponding to the high frequency pattern and a second read amplitudecorresponding to the low frequency pattern, and determining a head wearmetric according to the first read amplitude and the second readamplitude. A computer program product and computer system correspondingto the above method are also disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting one embodiment of a head monitoringsystem in accordance with the present invention;

FIGS. 2A-2C depict examples of test patterns in accordance with thepresent invention;

FIG. 3 is a flowchart depicting one embodiment of a head wear monitoringmethod in accordance with the present invention; and

FIG. 4 is a block diagram depicting one example of a computing apparatus(i.e., computer) suitable for executing the methods disclosed herein.

DETAILED DESCRIPTION

Embodiments of the present invention relate generally to magnetic tapedata storage, and more specifically, to monitoring the condition of tapeheads. Over time and depending on usage, tape heads may deteriorate,resulting in a higher read/write error rate, data loss, and even drivefailure. Currently, there is no means of measuring head-to-tape spacingwhile operating the drive. The head-to-tape spacing can indicate thedegree to which a tape head has worn down. Therefore, it is desirable tocome up with a metric for measuring and monitoring the condition of atape head.

It should be noted that references throughout this specification tofeatures, advantages, or similar language herein do not imply that allof the features and advantages that may be realized with the embodimentsdisclosed herein should be, or are in, any single embodiment of theinvention. Rather, language referring to the features and advantages isunderstood to mean that a specific feature, advantage, or characteristicdescribed in connection with an embodiment is included in at least oneembodiment of the present invention. Thus, discussion of the features,advantages, and similar language, throughout this specification may, butdo not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize that theinvention may be practiced without one or more of the specific featuresor advantages of a particular embodiment. In other instances, additionalfeatures and advantages may be recognized in certain embodiments thatmay not be present in all embodiments of the invention.

These features and advantages will become more fully apparent from thefollowing drawings, description and appended claims, or may be learnedby the practice of the invention as set forth hereinafter. The presentinvention will now be described in detail with reference to the figures.

FIG. 1 is a block diagram depicting one embodiment of a head monitoringsystem 100 in accordance with the present invention. As depicted, thehead monitoring system 100 includes tape drive 110, head element 120,resolution determining module 130, resolution estimating module 140,storage 150, cartridge 160, and patterned media 170. The tape drive 110may read a test pattern provided by the cartridge 160 in order tomonitor the condition of the head element 120.

Tape drive 110 may be a data storage device that reads and writes dataon a magnetic tape. In some embodiments, a cartridge, such as cartridge160, must be mechanically inserted into tape drive 110 in order for thetape drive 110 to operate. Tape drive 110 may read and/or write to acartridge's magnetic tape using head element 120; over time, this actionwears down head element 120.

Head element 120 may be any sort of tape head, which is a type oftransducer used in tape recorders to convert electrical signals tomagnetic fluctuations and vice versa. In some embodiments, the conditionof a head element 120 is determined by measuring the head-to-tapespacing in a tape drive 110. Head element 120 may include one or moretypes of tape heads, such as rotating heads, erase heads, Osbourneheads, and/or any sort of head know to those skilled in the art.

Cartridge 160 may be any sort of cartridge or cassette that is readableby tape drive 100. In some embodiments, cartridge 160 is a cleaningcartridge, which cleans the head element 120 when inserted into tapedrive 110. Cartridge 160 may be a cleaning tape or a diagnostic tape. Insome embodiments, cartridge 160 is a data tape that is not constantly inuse since usage can cause degradation of the cartridge. When cartridge160 is inserted into tape drive 110, head element 120 may read a testpattern from patterned media 170. Patterned media 170 may contain one ormore test patterns. In some embodiments, patterned media 170 is a lengthof magnetic storage tape upon which test pattern(s) are written.Patterned media 170 may be a transmitting head that transmits testpatterns stored elsewhere on cartridge 160 while cartridge 160 simulatesplayback by a system of gears or a drive belt connects the tape drive110's motor to a wheel inside the cartridge 160, similar to a cassettetape adaptor.

In some embodiments, each test pattern consists of one or morepredetermined low frequency patterns and high frequency patterns. As (orafter) the head element 120 reads the test pattern(s), the head element120 may communicate information to the resolution determining module130. Resolution determining module 130 may receive information relatingto the test pattern(s) and calculate resolution, which is directlyrelated to the head-to-tape spacing. Resolution may be calculated bydividing the amplitude of a high frequency test pattern by the amplitudeof a low frequency test pattern according to the equation:Resolution=Amplitude of high frequency test pattern/Amplitude of lowfrequency test pattern

When the amplitudes of both high- and low-frequency test patterns arethe same, then an ideal head will report that the resolution is equal to1.0; a lower value, such as 0.4, may indicate that there is significanthead wear. In some embodiments, resolution determining module 130receives the values of the amplitudes from the head element 120. As thehead element 120 wears over time, the spacing loss increases and thusthe head element 120 is unable to read the full extent of the highfrequency test pattern's amplitude. Thus, over time, the numerical valueof the resolution may decrease.

Resolution estimating module 140 may estimate head wear over time. Insome embodiments, resolution estimating module 140 applies statisticaltechniques to extrapolate the head element 120's future resolutionvalues based on a combination of prior resolution values, time elapsed,and/or tape drive 110 usage. For example, if a head element 120 has aresolution value of 0.9, and then after 1000 hours of tape drive 110activity, 0.8, resolution estimating module 140 may determine that afteranother 1000 hours of usage, head element 120's resolution value will be0.7. Any number of statistical techniques that extrapolate future valuesbased on a history of past values may be employed by resolutionestimating module 140, such as linear extrapolation, polynomialextrapolation, conic extrapolation, exponential curve extrapolation,logarithmic extrapolation, and the like. Resolution estimating module140 may receive past resolution values from storage 150, which storesand shares data regarding the resolution with the rest of headmonitoring system 100. In some embodiments, storage 150 receivesresolution values from head element 120 and/or resolution determiningmodule 130. Resolution estimating module 140 may also store futureresolution values in storage 150.

FIGS. 2A-2C depict examples of test patterns 200, 230, and 240 inaccordance with the present invention. As depicted, test patterns 200,230, and 240 include a low frequency pattern 210, high frequency pattern220, low frequency pattern amplitude 250, and high frequency patternamplitude 260. Test pattern 200 may represent a pattern as read by anewer head, whereas test patterns 230 and 240 may represent patternsread by a head experiencing head wear.

FIG. 2A depicts an example of a waveform read by a head with little tono spacing loss (head wear), whereas FIG. 2B depicts a waveform as readby a head with large spacing loss. As a head becomes worn, the abilityto read a high frequency pattern 220 is impacted before the ability toread a low frequency pattern 210. In particular, the amplitude value ofthe high frequency pattern 220 is affected because the worn head isunable to read the full extents of the test pattern's amplitude.

Resolution may be calculated by dividing the high frequency patternamplitude 260 by the low frequency pattern amplitude 250. By usingempirical evidence, resolution values may be meaningfully correlatedwith head wear. In some embodiments, the high frequency pattern 220 hasa frequency four times greater than the low frequency pattern 210. Thisfrequency difference can be achieved if the period at which the patternsare written is 2T for the high frequency and 8T for the low frequency(as period is inversely proportional to frequency). In such embodiments,it may be determined that tape drives start their life having aresolution of 0.6-0.8, and that a resolution of 0.4 or lower can resultin permanent read/write errors or outright head failure.

FIG. 3 is a flowchart depicting one embodiment of a head wear monitoringmethod 300 in accordance with the present invention. As depicted, thehead wear monitoring method 300 includes reading (310) patterns,determining (320) pattern amplitudes, determining (330) resolution,predicting (340) future resolution, and notifying (350) a user. Byreading known patterns from a test cartridge, the condition of a drivehead may be tracked over time, allowing a user to foresee and avoiddrive failure.

Reading (310) patterns from a cartridge may include reading testpatterns from a cassette or cartridge. In some embodiments, the testpatterns are encoded in the patterned media 170 of cartridge 160. Readpatterns may appear as the patterns depicted in FIGS. 2A-2C. Determining(320) pattern amplitudes may include measuring the distance from acenter line of a waveform to a peak of a waveform, as depicted byamplitudes 250 and 260 in FIG. 2C. In some embodiments, the amplitudedetermining operation 320 is performed by head element 120 and/orresolution determining module 130. The pattern reading operation 310 maybe performed while a tape drive is cleaned if the cartridge 160 is acleaning cassette.

Determining (330) a resolution value may include dividing the amplitudeof a high frequency pattern by the amplitude of a low frequency testpattern. In some embodiments, the resolution determining operation 330is performed by the resolution determining module 130. Resolution valuescorresponding to a head element may be tracked over time and stored,e.g., in storage 150. For a test pattern having a high frequency patternof four times the frequency of a low frequency pattern, a resolution ofbetween 0.6 and 0.8 may translate to a functioning tape head, whereas aresolution of 0.4 or below may indicate that the tape head isapproaching its end of life.

The resolution value may be calculated before and after a cleaning cyclein order to determine the efficacy of the cleaning cycle. A cleaningcycle may be requested by the tape drive due to data tapes leavingdeposits on the head that result in sudden poor error rates. Before thecleaning cycle is initiated, a quick snapshot of the head resolution maybe captured. At the end of the cycle, the resolution may be measuredagain. If the resolution values taken before and after cleaning fail toshow a noticeable change, it may be concluded that the cleaning wasineffective, or that a new cleaning cartridge ought to be used.Alternatively, if the resolution value after cleaning is higher than theresolution value before cleaning, the cleaning cycle may be determinedto be successful. In some embodiments, additional cleaning cycles may berequested until the pre- and post-cleaning resolution values stabilize.This may indicate that the cleaning tape was effective in removing thedeposits on the head to the best of its ability.

Predicting (340) future resolution values may include predicting theresolution of a tape at some point in the future, either as measured bytime elapsed, or usage time of the tape drive. In some embodiments, theresolution estimating module 140 is able to predict future resolutionsby drawing on resolution data stored in storage 150 and extrapolating.

Notifying (350) a user may include indicating to a user the status ofthe tape head. In some embodiments, the resolution value of a tape headmay be communicated to a user. The user may be alerted as to futureresolution values and/or when the head monitoring system 100 predictsthat the tape head will reach a certain condition or fail. The user maybe notified of the approximate number of usable hours and minutes leftin a particular tape head. In some embodiments, the user is notifiedthat the current resolution is too low to perform a particular back-upwithout hazarding the risk of the head wearing out before the back-up issuccessfully completed. The drive may be sequestered, or a warning maybe posted to the user asking if the user wants to proceed with a back-updespite a risk of tape head failure before successful completion of theback-up.

FIG. 4 is a block diagram depicting components of a computer 400suitable for executing the methods disclosed herein. It should beappreciated that FIG. 4 provides only an illustration of one embodimentand does not imply any limitations with regard to the environments inwhich different embodiments may be implemented. Many modifications tothe depicted environment may be made.

As depicted, the computer 400 includes communications fabric 402, whichprovides communications between computer processor(s) 404, memory 406,persistent storage 408, communications unit 412, and input/output (I/O)interface(s) 414. Communications fabric 402 can be implemented with anyarchitecture designed for passing data and/or control informationbetween processors (such as microprocessors, communications and networkprocessors, etc.), system memory, peripheral devices, and any otherhardware components within a system. For example, communications fabric402 can be implemented with one or more buses.

Memory 406 and persistent storage 408 are computer readable storagemedia. In the depicted embodiment, memory 406 includes random accessmemory (RAM) 416 and cache memory 418. In general, memory 406 caninclude any suitable volatile or non-volatile computer readable storagemedia.

One or more programs may be stored in persistent storage 408 forexecution by one or more of the respective computer processors 404 viaone or more memories of memory 406. The persistent storage 408 may be amagnetic hard disk drive, a solid state hard drive, a semiconductorstorage device, read-only memory (ROM), erasable programmable read-onlymemory (EPROM), flash memory, or any other computer readable storagemedia that is capable of storing program instructions or digitalinformation.

The media used by persistent storage 408 may also be removable. Forexample, a removable hard drive may be used for persistent storage 408.Other examples include optical and magnetic disks, thumb drives, andsmart cards that are inserted into a drive for transfer onto anothercomputer readable storage medium that is also part of persistent storage408.

Communications unit 412, in these examples, provides for communicationswith other data processing systems or devices. In these examples,communications unit 412 includes one or more network interface cards.Communications unit 412 may provide communications through the use ofeither or both physical and wireless communications links.

I/O interface(s) 414 allows for input and output of data with otherdevices that may be connected to computer 400. For example, I/Ointerface 414 may provide a connection to external devices 420 such as akeyboard, keypad, a touch screen, and/or some other suitable inputdevice. External devices 420 can also include portable computer readablestorage media such as, for example, thumb drives, portable optical ormagnetic disks, and memory cards.

Software and data used to practice embodiments of the present inventioncan be stored on such portable computer readable storage media and canbe loaded onto persistent storage 408 via I/O interface(s) 414. I/Ointerface(s) 414 may also connect to a display 422. Display 422 providesa mechanism to display data to a user and may be, for example, acomputer monitor.

The programs described herein are identified based upon the applicationfor which they are implemented in a specific embodiment of theinvention. However, it should be appreciated that any particular programnomenclature herein is used merely for convenience, and thus theinvention should not be limited to use solely in any specificapplication identified and/or implied by such nomenclature.

The embodiments disclosed herein include a system, a method, and/or acomputer program product. The computer program product may include acomputer readable storage medium (or media) having computer readableprogram instructions thereon for causing a processor to carry out themethods disclosed herein.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowcharts and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

What is claimed is:
 1. A method, executed by a computer, for monitoringhead wear, the method comprising: reading from a cartridge a firstpattern and a second pattern, wherein the first pattern is a higherfrequency pattern and the second pattern is a lower frequency pattern,and wherein the higher frequency pattern has a frequency that is atleast four times greater than a frequency of the lower frequencypattern; determining a first read amplitude corresponding to the firstpattern and a second read amplitude corresponding to the second pattern;determining a head wear metric according to the first read amplitude andthe second read amplitude; determining a future head wear metricaccording to a head wear metric history; determining a first resolutionbefore a cleaning cycle, wherein the first resolution is determined bydividing the first read amplitude by the second read amplitude;determining a second resolution after the cleaning cycle, wherein thesecond resolution is determined by dividing the first read amplitude bythe second read amplitude; comparing the first resolution and the secondresolution; notifying a user that the head wear metric is between aresolution of 0.6 and 0.8 in response to determining that the resolutionis between 0.6 and 0.8, wherein the resolution is determined by dividingthe first read amplitude by the second read amplitude; notifying a userthat the head wear metric is at or below a resolution of 0.4 in responseto determining that the resolution is below 0.4; and notifying a user ofthe head wear metric.